This study assessed the possible impact of a former ferrochromium plant in Siechnice (Lower Silesia, Poland) on water reservoirs and living organisms. The metal concentrations (Zn, Cu, Pb, Fe, and Cr) in the sediments were determined, along with ecotoxicological studies that were conducted on both the sediments and the surface water of three water bodies that border the slag heap. The samples of the sediments and water were taken at different distances from the landfill area. The studies also covered a human health risk assessment. The highest concentrations of all the studied elements were observed in the sediments taken from the water reservoir closest to the landfill. In the case of the sediments, a 30% death rate for Heterocypris incongruens (Ostracodtoxkit F) was recorded at the same site. Additionally, at this site, the ecotoxicological studies on the surface water revealed the highest mortality for Daphnia magna (Daphtoxkit F magna) and the lowest values of LC50 for algae (Algaltoxkit). The health risk assessment of the sediments was estimated by calculating the noncarcinogenic health risk using the hazard quotient (HQ) and hazard index (HI), and the carcinogenic risk was calculated using the excessive risk of cancer development (ECR) measurement. The hazard index (HIing) for Cr exceeded 1 for children, which suggests that possible adverse health effects might occur for humans. The ECR values calculated for Cr and Pb were above the range limit of 10−⁶. The value for Cr was the highest for the sediments from the closest water reservoir to the landfill for both children and adults. Studies prove that the water reservoirs located near landfills pose potential ecological risks, and the risk is the highest where the distance is the shortest from the slag heap. In prospective human health risk assessments, the sediments from the closest water body pose a potential carcinogenic health risk to humans, especially to fish consumers, i.e., the residents of neighboring areas who might experience severe health problems from the intake of Cr and Pb through fish consumption. Significant steps should be taken to reduce Cr concentrations in the sediments to minimize the risk of human health adverse effects.

The studies of the impact of post-metallurgical landfill were conducted in Siechnice near Wrocław, Lower Silesia. The samples of sediments and water were taken at different distances from the slag heap area. We assessed the metal concentrations in the samples, then ecotoxicological tests were conducted as well. Ostracodtoxkit F was performed to measure the toxicity of sediments. Daphtoxkit F magna and Algaltoxkit F tests were performed to evaluate water quality. 30% mortality rate of H. incongruens (Ostracodtoxkit F) was recorded in sediment studies in the closest site to the waste dump. The highest mortality rate of D.magna in 100% dilution after 48 hours was observed in water samples taken from the closest distance to slag heap, and the death rate did not exceed 50%, therefore it was not possible to establish LC50. The concentrations of selected heavy metals (Zn, Cu, Pb, Fe, Cr) were determined in sediment samples. It was found that the closest site to the landfill was moderately/heavily polluted with Cr according to LAWA classification. The health risk assessment of the sediments was estimated by calculating non-carcinogenic health risk such as Hazard Quotient (HQ), Hazard Index (HI); and carcinogenic risk - Excessive Risk of Cancer Development (ECR). Hazard Index (HI ing) for Cr was exceeding 1 for children, implying possible adverse health effects might occur. ECR values for Cr and Pb were above the range limit of 10⁻⁶ in all sample points. But the cancer risk was found to be very low.